The present invention relates to a network forwarding apparatus, and more particularly to a router apparatus having a routing protocol for generating a routing table used to determine the destination of a packet to be transferred between communication terminals.
A router which forwards packets between communication terminals must accommodate a large number of lines. Conventionally, when there is a need to increase the lines as the network grows, routers must be added to the network and a configuration definition must be created for each added router.
Because there is no definite means for establishing an association of a plurality of routers that were added, a routing protocol usually used to transfer packets to or from other terminals has been used to exchange information among the plurality of routers.
However, the prior art described above has the following problems.
First, when routers are added as the network grows, the network forwarding function is executed by the plurality of routers. The plurality of routers form a router network, which requires a subnet. This results not only in the waste of network addresses but also in the reduction of address space available to users.
Second, each independent router requires that the configuration be defined for it (configuration definition); for example, the network interface addresses or the routing protocol execution parameters must be defined for each router. This increases the network management cost not only at configuration definition change time but also at production run time.
Third, a routing protocol performs version verification, route exchanging priority determination, and so on in order to exchange network information with other routers. The load of this processing is large enough compared with that of actual network information exchange. Thus, the routing protocol is not suitable for network information exchange among the routers which are added as lines are added; that is, it is not suitable for network information exchange in a closed environment. In some cases, the routing protocol also decreases the performance of terminal-to-terminal packet forwarding processing which is the fundamental processing of routers. The above-mentioned prior art is referred to in the following publication, for example: (1) Thomas M. Thomas II xe2x80x9cOSPF Network Design Solutionsxe2x80x9d Macmillan Technical Publishing pp. 129-202; (2) RFC:791 xe2x80x9cINTERNET PROTOCOL DARPA INTERNET PROGRAM PROTOCOL SPECIFICATIONxe2x80x9d September 1981, Pages (i)-(iii); (3) RFC1058, C. Hedrick xe2x80x9cRouting Information Protocolxe2x80x9d June 1988, pp. 1-6; and (4) RFC2178, J. Moy xe2x80x9cOSPF Version 2xe2x80x9d July 1997, pp. 1-6.
To solve the above problems, it is an object of the present invention to provide a highly-expandable router configuration technology which flexibly meets the need to increase lines as a network grows.
To achieve the above object, an aspect of the present invention provides network information sharing means in each router to allow network information collected by routing protocols running in a plurality of routers to be shared. Sharing network information by the plurality of routers makes them externally appear as if they were a single virtual router. In the following description, this virtual router is called a clustered router.
The routing protocol running in each router in the clustered router exchanges network information with other routers outside the clustered router and, when its own network information changes, notifies the network information sharing means of the change.
The network information sharing means, when notified of the information, generates a network information notification packet containing a routing protocol identifier and sends the packet to all routers in the clustered router. Upon receiving the network information notification packet, the network information sharing means extracts update information from the received packet and sends the extracted update information to the corresponding routing protocol means in accordance with the routing protocol identifier.
When the routing protocol means receives the update information, it updates its own network information with the received information.